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Tips from rear brake, p-brake, caliper rebuild

Over the weekend I put the car up on stands and did a bunch of things I had been putting off. One area of this was rear pads, rotors, parking brake rebuild and caliper rebuild. I wanted to share a couple of things "learned" during this process.

1/ Balo has been my go-to brand for rotors for some time. Balo now makes a coated series, similar to the Zimmerman CoatZ I suspect. I ordered these for the rear since I have read these coatings are more durable than painting the hats myself and it goes all or most of the way through the vent channels. It was indeed a stout, durable coating which appeared to be everywhere - even down the vents. I suspect this will dramatically reduce my salty-winter visible corrosion to the rotor edges and vents, as well as inside where the parking brake operates. They come at a bit of a premium but it looks good at this point.

2/ Various online writeups claim that after disconnecting the caliper, fluid will eventually stop running out. It will not. It will gravity bleed the reservoir dry if you're a slow worker on the caliper rebuild. Be careful, or clamp the lines. I elected not to clamp the lines to be sure not to damage them, but monitored throughout.

3/ Various write ups also say that installing the new dust boots on the calipers is a matter of popping it into the groove on the piston, pressing it into the caliper and poof, you're done. Wrong. When you tear into the fine print that comes with the dust boots you're supposed to use a special ATE seating tool to seat the boot onto the caliper. The boot is a smaller diameter than the area of the caliper it snaps onto in order to provide good lock in place. I did not have said ATE special tool nor any other socket or tin can of the right diameter. (As an afterthought, a properly sized hose clamp probably would have worked well - dial to the right size and tap away). I put the boot onto the closed side of the caliper first leaving the open side unseated. I then tapped lightly on the seal edge with a small dead-blow rubber mallet and that seemed to seat it. I could never get it quite as well seated as the one I pried off (before I knew it wasn't going to be easy to get back on). I don't know if the fronts are different/easier, but you have been warned.

4/ The parking brake - yow what a mess. The area behind the rotor needed lots of wire brushing and the interface between the steel and aluminum suspension had white corrosion. I cleaned it up as best I could, treated with rust converter, and painted with black paint. I don't know why all of this stuff isn't coated from the factory.

5/ All of the tips I saw on reassembling the parking brake were not fun or effective at all. I came up with something I thought worked quite well. I may not be the first to do it this way, but I hadn't read what I did anywhere else. For the rest of the parking brake I referenced a lot of material, but in particular I looked a fair bit at (change x to m) http://forums.bixxerforums.com/forum/showthread.php?t=1381731. I'll link a picture from there (if it works - if not: http://www.bixxerfest.com/forums/attachment.php?attachmentid=215151

I now disagree with that assembly order. What I ended up doing was assembling the adjuster (5), the lower spring (6) an the shoes off of the car. Then you can easily open the top and slide it into position from the bottom. I then set the spring loaded fasteners (2 and 7). Ensure that the tops of the shoes are resting on either side of the fixed metal at the top for support. Reinsert the cable lever mechanism and then install the top spring (4). Nothing but a pair of vise grips could provide the force and grab needed to pull this spring into place. You MUST use at least eye protection. I used a full face shield. When this stuff wants to fly around it will hurt - a lot.

6/ As I mentioned in another thread (http://bimmer.roadfly.com/bmw/forums/e39/9588778-1.html) I had some trouble bleeding. I possibly made a mistake near the MC but it's worth pointing out that rebuilding the calipers introduces a ton of air and stubborn bubbles. You will need to use extra pedal pressure while bleeding and tap the piston with a small mallet A LOT to keep encouraging bubbles. Eurodavid has also said he's had good luck with pre-filling the caliper while it's off the car.

7/ If you're replacing the p-brake shoes, also buy one of the full hardware kits with the springs and spring-loaded fasteners. It's much easier and nicer with all-new stuff and doesn't cost a lot more.

8/ If you're removing the caliper, break the torque set on the brake hose (14mm) before unbolting any part of the caliper. Don't forget to re-torque it after mounting everything back up.

9/ I have always been replacing the rubber slide bushings every time I do a brake job (every 5-7 years). It's cheap and refreshes a part which is integral to good pedal feel and even pad wear

10/ It's been 7 years since my rears were done and they were still wearing slowly and within spec. I found, however, that the backing plates on the piston side were starting to come apart and were flexing and cracking. The inner pad material was worn in a slight concave curve and the rear brakes were probably underperforming even though they weren't technically worn out. I should have done the rears with the fronts two years ago. If you have had your rears for a long time (regardless of miles) or are in a high corrosion environment (salt country, ocean side) keep an eye on this.

Re: Tips from rear brake, p-brake, caliper rebuild

some questions on your points:

2) is it not possible to put a flexible rubber plug in the rear line (like I did when I rebuilt the fronts). It plugs it instantly, holds like glue (you can swing the line around all you want, and it won't come out). Are the rear lines somehow different than the front lines? I have various size diameter plugs, so diameter is not an issue.

3) are you saying the rear boots are harder to get on than putting new boots on the front piston? That was a bear getting them on the front...grrrr. Dang, that definitely means I am going to be letting more cuss words fly at the BMW gods than I normally do ;-0

8) what are you using to set the torque on the brake lines? Do you have one of those open-ended torque wrenches, or are you using a dial gauge? I feel guilty that when it comes to torque settings that require an open-ended wrench, I've been going by feel (which we both know isn't worth a whole lot---so I sometimes compensate probably too loosely so as to not strip it or whatever)

10) you've got me wondering if I should have done mine a few years ago when I did the fronts and rebuilt them, new guides, bushings, pads, disc, etc. Dang, Craig, the rears have....well, uhmmm, have never been touched in the cars 15 year life (I adjusted the parking a bit 4 years ago, the nut still spun well). I sure hope in this all- year-long wet Belgian environment I live in, that stuff on there is not rust-welded to the car. Crap, I knew I was being lazy 3 years ago when I did the fronts and not the rears.

Thanks for the tips, especially the parking brake assembly. Will come in handy as I ordered those parking brake kits you mentioned, for when I do the whole rear thing hopefully next summer.

Re: Tips from rear brake, p-brake, caliper rebuild

Euro:

#2: Sure it would be possible to put something in there. I prepared for the job planning to clamp the line but thought better of it when the time came. I didn't have an expansive selection of rubber plugs so I elevated the end, wrapped in a rag and let it ooze.

#3: I didn't do the fronts when I did the brake job. The boots look fine and the calipers weren't having a problem so I didn't do them. I can't comment on whether the fronts are different than the rears but lots of writeups don't speak at all about taking any special action to seat those boots. If everyone follow those writeups they won't have a seal at all (unless the fronts just slip onto the caliper body super easy). Anyone without the caliper end of the boot fully seated would be better off leaving them alone. The more I think about it now, the more I wish I had thought of having a hose clamp of the right size on hand. I don't think I have any that big lying around. One would have to be careful not to cut the boot, of course, but I think it would function like the ATE "special tool". Maybe I'll scan and post the directions from ATE which illustrate the tool.

#8: Feel. I put on about what I took off. I don't have tools to do torque where open-ended wrenches are required. When I loosened mine they felt like what I would describe as "snug". (As you say, not worth a whole lot). You probably recall the thread is pretty fine and seals quickly. I think it spins about 10 turns or so before needing torque so the torque isn't crucial either the seal or for staying assembled. You have a far more calibrated touch than I anyways.

#10: I would definitely pull the caliper and take a look. As I mentioned my pad backing plates were corroding and looking "delaminated". The piston was starting to push through the backing plate and the pad was wearing concave. There was still braking action - my rear wheel got a little dusty and the rotors stayed shiny in the swept area, but I don't think it was really contributing to stopping the car. The main brakes were not a rust fest, just the backing plate. Everything disassembled easy-peasy. There was lots of flaky stuff in with the p-brake but nothing was stuck. The bearing hub was spotless (reassembled with a thin coating of anti-seize).

Just like in 2003 (my last full F/R brake job) I can feel the better stopping power with the rears done. They contribute in a way that doesn't feel obvious. There's less nose dive, less pedal effort, less of a feel of "hard braking" (probably all the bushings being squished in the front) but lots more stopping. It's like there's a chute or anchor out back. Too bad I have to put my snows on within a week. Braking is the first thing I miss when I switch to snows.

If your rear brakes are truly original I suspect you're going to want to change them. Most people won't need to replace the parking brake shoes but some "servicing" is a good thing from what I saw. A couple of years ago my p-brake stopped holding even when adjusted - the car would just keep rolling. I guess they got glazed or contaminated or something. I bought the parts to replace it all but it cleared up while they were in the mail. They've been in the basement ever since and I figured I might as well use them.

Getting rear caliper boots on is a piece of cake(m

They just pop over the lip on the outside of the caliper, I used a screwdriver blade to push them down.
Now the fronts are a royal PITA unless you have 3 hands. The boot fits inside a groove and then the piston gets pushed in, which keeps the boot in the groove.
With the piston in place you can't remove the front caliper boot.
Front caliper pic

Re: Getting rear caliper boots on is a piece of cake(m

In the case of the parts I was working with, the diameter of the new boot was enough smaller than the caliper that it couldn't just "pop on". Maybe there have been some revisions to the replacement boot part over time?

Other write ups made it sound like a piece of cake, and removing the old boot didn't make it seem like it was a tight fit (although it had been there for 13 years).

It didn't seem to be the wrong part or anything, but ATE called for the use of a special tool to seat the boot. I can sort of see why.

One day I'll have enough time to clean my calipers up all fancy like you :-P

Re: Tips from rear brake, p-brake, caliper rebuild

No I never did. As long as it was kept in adjustment it was holding well for quite some time. There is/was a lot of gnarly rust build up on the inside of the rotor where the shoes ride, even though I try to remember to pull the brake occasionally while a city street speeds to keep the drum clean.

It could have been a number of things. Perhaps it was just glazed, or perhaps some chunks of drum flaked off in a way that very little of the shoe was making contact but the adjustment was "proper". After more wear and flaking it was fixed again.... I'll probably never know. The old shoes seemed in OK shape with lots of material left and no cracking.

No, they are the original color, black.

"Drive It Like You Stole It, A Sickness for Quickness"The Bottle Rocket "King of Spray" 2 Stage Nitrous OxideDare to be different and stand out among the crowd of me-to-cars!No guts, no glory!Tire smoke, not traction control!Zionsville all aluminum radiator to replace the 3 leak prone Nissens Radiators!

Thks, Jim. I did the same as you. Glad 2 know

Re: Tips from rear brake, p-brake, caliper rebuild

Craig,

You've got me itching to do my rears now, even if I am wary of what I might find. When you said "it gives the car better stopping control/power", that immediately sells in my mind (at least over here). Have enough to worry about (from other drivers) when wanting to keep my old girl between 160-200kmph on the autobahns; that piece of mind & help from having the rears done is a no-brainer now that I think about it fully, and I am kicking myself I didn't do it when I had the chance.

Oh, on the pad. I thought you were talking about (

the backing plate behind the rotor, which isn't even in the pic.
Yes I did paint that too, in an attempt to make it match the car and wheel.
I just hate rusty calipers, pads, and rotors, it ruins the looks of a good driving machine.